I give a gentle wipe under the edges when using Lemon Pledge on the tank, and haven't noticed any marks after 2 1/2 years. I slather mine with Dubbin or mink oil once a year over winter storage.
Fred.
What he said.

I have a black tank with a Talisman bid.
Mine has been on there for a couple years now too and no problems. I've had it off the bike a couple times since putting it on and haven't noticed anything.
Did wax the tank with a good carnauba wax. Hit the tank every once in a while with a detailer/cleaner. Usually just lift up the edge of the bid and wipe under it.